Well since the first revision isn't even out yet I think this question is premature. Once you have the money saved up then maybe ask the question, but again apple plays close to the vest. Just look at the PB forum, eveyone expected a speedbump in the 12 and a new 15"pb at the developers conference.
The bottom line get the computer that best suits your needs now with money that you have (or will have) and don't sweat what's coming around the corner because there always will be a newer computer coming soon.
Mike